1. Field of Invention
This invention relates broadly to surgery and surgical devices. Particularly, this invention relates to intramedullary implants for fixation of fractures of the mandibular condyle and methods for using the same.
2. State of the Art
Fractures of the mandibular condyle are common, comprising almost a third of all mandible fractures. Treatment of mandibular fractures focuses on reduction of the fracture and rigid fixation to allow for osteosynthesis. This can be accomplished with maxillomandibular fixation, internal fixation, or both. Open reduction and internal fixation (ORIF) has become the preferred method of treatment for many mandibular fractures because it can restore the load-bearing properties of the bone and allow for a quicker return to function. This technique can be applied to fractures of the mandibular condyle through transcutaneous incisions or through an intraoral incision using endoscopes. Both of these approaches can provide adequate surgical access; however, each has its disadvantages.
External approaches carry the risk of injury to one or more branches of the facial nerve salivary fistula, Frey's syndrome, and hypertrophic scarring. Current ORIF techniques employ plates and screws applied to the external bone surface. It is difficult to apply the screws at the requisite 90 degree angle without a transbuccal puncture incision when using these plates. Improper screw placement, insufficient bone stock on the proximal fragment, and failure (bending or fracture) of the plate have been encountered with traditional miniplate implants.
Endoscopic mandibular condyle repair techniques have aided in the treatment of many condylar and subcondylar fractures in recent years. The use of endoscopes to apply traditional miniplates still requires a transbuccal puncture and carries the potential for facial nerve injury; however, there has been a much lower incidence of facial nerve paresis than in traditional “open” surgical approaches. Endoscopic repair is most readily applied to fractures that are in the subcondylar region, where there is adequate bone to hold two screws proximal and distal to the fracture line. However, this technique is more difficult to apply to fractures that are through the condylar neck, where it is more challenging to keep the fracture reduced, place the plate, and insert the screws properly due to the small size of the proximal bone fragment.
For these reasons, many surgeons opt to treat mandibular condyle fractures with extended maxillomandibular fixation; a treatment that is itself associated with potential morbidity including inadequate reduction of the fracture, discomfort, prolonged loss of function, joint ankylosis, risk of aspiration, and death.
Intramedullary fixation is a technique that has been utilized by orthopedic surgeons in the treatment of certain fractures of long tubular bones in the body including the femur, tibia, clavicle, and radius. Intramedullary fixation has been attempted in the mandibular condyle in the form of Kirschner wires (K-wire) inserted along the entire length of the mandibular ramus and condyle as well as lag screws drilled through cortical bone. As with intramedullary fixation of long bone fractures, previous attempts at intramedullary fixation of the mandibular condyle have relied on insertion of implants or a guide wire through healthy bone distant to the fracture (for example; through the epiphysis or through a joint). The anatomy of the face and jaw makes this technique impractical. Successful application of a K-wire to the mandibular condyle requires a submental neck incision and an intact and straight intramedullary canal. The intramedullary canal often does not meet these requirements due to the natural curvature of the ramus and variations in the intramedullary space. Furthermore, a K-wire has a smooth surface and does not engage either side of the fractured bone. Therefore, it does not actually provide fixation of the fracture. Lag screws do provide fixation of the fracture but require application through cortical bone, in some cases at an acute angle to the intramedullary axis of the bone. Furthermore, both K-wires and lag screws require facial or neck incisions (invasive approach) which increase the risk of surgical morbidity as previously discussed.